Intracorporeal devices are devices suitable for introduction into a patient's body, for example, into a body lumen of a patient. Many clinical procedures require the insertion of wires, tubes, probes or other objects into a body lumen of a patient. For example, guidewires and catheters may be used for gaining access to the coronary vasculature, as in an angiogram or in angioplasty. A guidewire is a thin, flexible device used to provide a guiding rail to a desired location within the vasculature (or other body cavity) of a patient. A balloon catheter is a device with an interior lumen with at least a portion of the catheter being able to expand. In coronary angioplasty, a balloon catheter, guided by a guidewire, is positioned within a partially-occluded coronary artery where its balloon portion is expanded in order to press against and enlarge the lumen of a blood vessel in which it is situated. Alternatively, endoscopy requires the introduction of an endoscope into the lumen of a patient, as may be done during a colonoscopy.
Imaging of internal body lumens provides clinicians with information useful in many clinical situations and procedures. Imaging may be accomplished using electromagnetic radiation (such as, e.g., optical radiation, infrared radiation, and radiofrequency radiation). For example, where a patient is suspected of having an occlusion in an artery, optical imaging of the artery and the artery wall can provide information about the type, severity and extent of an occlusion or lesion and so improve the diagnosis and treatment of the patient. Intracorporeal imaging is useful for the placement of guidewires, catheters, endoscopes, and other instruments in desired locations within a patient's body, typically within a body lumen.
The ability to decide where to locate a catheter during a clinical procedure can be improved by providing interior images of the body lumen, such as the blood vessels during angioplasty or the colon during colonoscopy. It is often critical to the success of an angioplasty procedure that a balloon catheter be properly located within a blood vessel. Thus, imaging by guidewire, catheter, or other such device can be of great importance to the success of the procedure.
Imaging endoscopes, guidewires and catheters have been described, as in U.S. Pat. Nos. 5,321,501 and 5,459,570 to Swanson et al., and U.S. Pat. No. 6,134,003 to Tearney et al. Catheters adapted for optical imaging using non-visible light may be useful as well, as disclosed in U.S. Pat. No. 5,935,075 to Cassells et al. Such imaging devices typically use an optical fiber to carry light. Imaging systems may be used to obtain image information from within a body lumen, as discussed by Swanson et al. and Tearney et al., and may be used to obtain image information from peripheral tissues as well, such as teeth, as discussed by Nathel et al., U.S. Pat. No. 5,570,182. All patents and patent applications, both supra and infra, are hereby incorporated by reference in their entirety.
Optical imaging of internal lumens may be performed using endoscopes, guidewires, and catheters. One method useful for optical imaging is termed “optical coherence tomography” (OCT). OCT utilizes optical interference between two halves of a split optical beam to detect small differences in path-length between light reflected from a fixed surface and light reflected from an object to be imaged, as described, e.g., in U.S. Pat. No. 6,134,003 to Tearney et al. OCT may be used with intracorporeal instruments to image within a body lumen. OCT typically uses a short coherence-length light source, and a single-mode optical fiber is typically used to direct and to carry the optical radiation. In addition, an OCT system may include such other components as an interferometer, an optical radiation detector, a reference optical reflector, and a beam director to direct or rotate the optical beam. The beam director may include a prism, a lens, or a mirror.
In OCT, a beam divider is used to divide the optical radiation from an optical radiation source along a first optical path to a reflector and along a second optical path to the structure being viewed. An optical radiation detector is positioned to receive reflected optical radiation from the reflector and reflected optical radiation from the structure and to generate a signal in response to the reflected optical radiation. The signals from the detector may be utilized to generate an image or to obtain other information about the structure being viewed.
An optical fiber or bundle of fibers may be used to carry optical radiation. Optical fibers may be part of an optical assembly, and may be clad or wrapped with other materials for strength and to improve the efficiency of optical transmission. A ferrule may be attached to an end of the optical fiber to strengthen and protect the optical fibers, and to facilitate the attachment of optical fibers to other optical instruments.
An imaging instrument typically has a window to allow optical access between the exterior of the device and an optical fiber or light path within the device. In addition, an optical fiber, or the entire optical instrument, may be rotated within an internal lumen to provide a complete optical scan of a region of the lumen.
The optical path of an optical imaging instrument for use within a body lumen must connect to other instruments in order to pass optical information to other instruments and ultimately to an operator. Thus, the optical path must be configured to operably connect with other optical instrumentation external to the patient's body. Thus, it is often advantageous to have a window in an imaging catheter, imaging guidewire (IGW), endoscope, or other imaging probe to allow optical access between the exterior of the device and the optical fiber or light path within the device. U.S. Pat. No. 6,134,003 to Tearney et al. discloses a rigid plastic clear window.
In coronary angioplasty, a guidewire and an angioplasty catheter are threaded through a patient's vascular bed to bring the distal ends of the guidewire and catheter to and beyond the site of the lesion. For effective use of a balloon angioplasty catheter, the distal end of the balloon angioplasty catheter preferably extends to a position distal to the lesion. For this reason, it is vital that the clinician have accurate knowledge of the extent of the lesion and the condition of the lumen wall.
To do so, the imaging instrument must be located within the body lumen containing the lesion, positioned adjacent or near to the lesion. Typically, an imaging instrument will be advanced distally into the lumen, until a lesion is encountered. The instrument will often be advanced further distally to determine the extent and margins of the lesion, and to position therapeutic instruments across the lesion so that the entire lesion may be treated.
After such distal positioning within a lumen across a lesion, where a clinician wishes to observe or document the condition of a body lumen during an invasive procedure, an imaging instrument may be retracted proximally (“pulled-back”) to scan the lumen in order to display real-time images of the lesion and lumen wall. Such a pull-back scan may take more than one and a half minutes. In many instances a clear saline wash solution is used to remove or dilute blood within the lumen in the region around the imaging apparatus in order to provide better visualization of the vessel walls. However, such a saline wash introduce large volumes of fluid into the patient. Saline does not carry as much oxygen as blood, so that excessive amounts may reduce oxygenation within a patient's tissues, and increasing blood volume may stress the heart, so that excessive washing may be harmful to a patient. High intensity illumination within a body lumen, using visible light or other radiation, including ultrasound radiation, may be used in an attempt to improve the quality of images obtained in saline and to obtain better images through blood or partially-diluted blood. However, intense radiation within a body lumen may be harmful to a patient's tissue, particularly if the tissue is exposed to such radiation for a minute and a half or more.
As a result, prior art methods present clinicians with the poor choices of either limiting illumination intensity and exposure time in consideration of patient health and comfort, resulting in poor quality images, or ignoring patient health and comfort by using higher intensity illumination and longer exposure times, resulting in possible tissue damage. Accordingly, devices and methods for obtaining high quality images from within a body lumen while minimizing damage and stress to the patient are desired.